Welded assemblies and methods of making welded assemblies

ABSTRACT

A welded assembly includes a first sheet and a second sheet. The second sheet is disposed over a portion of the first sheet and defines an overlap portion between the first and second sheets. A weld fastening the second sheet to the first sheet in the overlap area connects the second sheet to the first sheet for distributing stress uniformly across a welded portion of the overlap area.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. §119(e)to U.S. Provisional Application No: 61/881,623, filed Sep. 24, 2013,which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to welded assemblies, and moreparticularly to welded joints for coupling hot sheets and cold sheetssuch as in hot sections of gas turbine engines.

2. Description of Related Art

Gas turbine engine hot section interiors can operate at extremely hightemperatures. They typically include a liner that is directly exposed toa flow of hot combustion gases during engine operation for extendedperiods. The liner, i.e. a hot sheet, is typically a sheet metalstructure surrounding the combustion flow space aft of where fuel andoxidizer flows are mixed and ignited prior to being passed to theturbine section. In certain engines an outer liner, e.g. a cold sheet,envelopes the hot sheet. The cold sheet is spaced away from the hotsheet such that a plenum is defined between the outer surface of the hotsheet and the inner surface of the cold sheet. Working fluid, typicallyair, is extracted from the compressor section of the engine and flowsthrough the plenum between the cold sheet and the hot sheet for purposecooling the hot sheet.

The hot sheet requires structure to fix the hot sheet within the engine.Generally, hot sheets couple to engine structure using sheet metalstructures attached the hot sheet outer surface. In hot sectionsincluding cold sheet and hot sheet portions, these sheet metalstructures extend through the plenum and form joints on opposite ends atthe inner surface of the cold sheet and outer surface of the hot sheet.Because the stress imposed on the coupling structure, the respectivejoints on the cold sheet and hot ends are generally formed by a brazingprocess. Due to extreme temperatures and materials from the cold, hotsheet, and coupling body are constructed theses brazes are typicallyrelatively costly nickel or gold-nickel brazes.

Conventional brazed joints have generally been considered satisfactoryfor their intended purpose. However, there is a continuing need toreduce cost and complexity of engine manufacture. There also remains aneed for lightweight joints for applications such as those describedabove. The present disclosure provides a solution for these problems.

SUMMARY OF THE INVENTION

A welded assembly includes a first sheet and a second sheet. The secondsheet is disposed over a portion of the first sheet and defines anoverlap portion between the first and second sheets. A weld in theoverlap area connects the second sheet to the first sheet. The weld isconfigured and adapted for reducing peak stress and smoothing the stressdistribution within the weld and overlap area of the sheets.

In certain embodiments, the second sheet is a coupling member forsupporting a liner in a gas turbine engine hot section. The first sheetcan be a hot sheet of a gas turbine hot section. The first sheet can bea cold sheet associated with a gas turbine hot section. A Z-bandcoupling a hot sheet to a cold sheet of a gas turbine engine can formthe second coupling member. The welded assembly can form a lap jointcoupling the first and second sheets to one another.

In accordance with certain embodiments, the weld includes a weld linetracing a linear shape in the overlay area. In accordance with certainembodiments, this can include a weld line tracing an arcuate segment inthe overlay area. The weld can further include second and a thirdarcuate weld line segment disposed on opposite ends of the first arcuateweld line segment wherein the second and third segments have differentcurvatures from the first arcuate segment.

It is contemplated that the weld can include a weld line tracing anelliptical segment in the overlay area. The second sheet can include alaterally extending bend line extending parallel to the major axis ofthe ellipse. The elliptical segment can open in a direction opposite thebend line. A distance between the weld line and the bend line can beabout a quarter the length of the minor radius of the ellipse. An end ofthe weld line can be offset from a lateral edge of the second sheet by adistance about one and a half times the minor radius of the ellipse. Theelliptical weld line segment can be centered with respect to a loadingaxis of the second sheet.

A gas turbine hot section includes a welded assembly as described above.The first sheet is a combustion gas space liner and the second sheet isa z-band for coupling the liner within the engine. The weld includes aweld line tracing an elliptical segment in the overlap area, and thesecond sheet includes a laterally extending bend line parallel to themajor axis of the ellipse such that the elliptical segment opens indirection opposite the bend line. A distance between the weld line andthe bend line is about a quarter the length of the minor radius of theellipse and a distance between an end of the elliptical segment and alateral edge of the second sheet is about one and a half times thelength of the minor radius of the ellipse. The elliptical segment iscentered with respect to a loading axis of the second sheet.

A method of forming the welded assembly described above includesoverlapping a portion of the first sheet with the second sheet andforming a weld fastening the first sheet to the second sheet by tracingan elliptical weld line in the overlap area. The weld is formed using alaser welding process.

It is contemplated that the second sheet includes a bend line and themethod include defining the weld line an offset distance about a quarterof the minor radius of the ellipse. The weld line can be offset by aboutone a half times the minor radius of the ellipse from an edge of thesecond sheet.

The foregoing features and elements may be combined in variouscombinations without exclusivity unless expressly indicated otherwise.These features and elements, as well as the operation thereof, willbecome more apparent in light of the following description and theaccompanying drawings. It should be understood, however, that thefollowing description and drawings are intended to be exemplary innature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a partial cross-sectional side view of an exemplary embodimentof a gas turbine engine, showing the engine hot section;

FIG. 2 is a cross-sectional side view of a portion of a hot sheetcoupled to a cold sheet, showing a coupling extending between the hotsheet and the cold sheet;

FIG. 3A is perspective view of a lap joint, showing a linear weld;

FIG. 3B is a plan view of the weld of FIG. 3A, showing a linear weldline;

FIG. 3C is a contour map showing stress distribution in the lap joint ofFIG. 3A, showing peak stress points in opposing ends of the weld andstress distribution in the joint;

FIG. 4A is perspective view of a second lap joint, showing an arcuateweld;

FIG. 4B is a plan view of the weld of FIG. 4A, showing an arcuate weldline;

FIG. 4C is a contour map showing stress distribution in the lap joint ofFIG. 4A, showing peak stress locations and stress distributionassociated with a load applied to the assembly;

FIG. 5A is perspective view of a third a lap joint, showing anelliptical weld;

FIG. 5B is a plan view of the weld of FIG. 5A, showing an ellipticalweld line;

FIG. 5C is a contour map showing stress distribution in the lap joint ofFIG. 5A, showing peak stress points and stress distribution in thejoint; and

FIG. 6 is a chart showing relative stress for a load within the linearweld, arcuate weld, and elliptical weld of FIG. 3A, FIG. 4A, and FIG.5A, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a gas turbineengine including a lap joint in accordance with the disclosure is shownin FIG. 1 and is designated generally by reference character 100. Otherembodiments of lap joints in accordance with the disclosure, or aspectsthereof, are provided in FIGS. 2-6, as will be described. The systemsand methods described herein can be used in lap joints for supportingcombustion gas space liners in gas turbine engines, such as at hot sheetand cold sheet connections for example.

With reference to FIG. 1, a gas turbine engine 10 is shown. Gas turbineengine 10 includes low-pressure spool 12 and a high-pressure spool 14.Low-pressure spool 12 includes a low-pressure compressor 16 andlow-pressure turbine 18 connected by low-pressure shaft 20.High-pressure spool 14 includes a high-pressure compressor 22 andhigh-pressure turbine 24 connected by high-pressure shaft 26. A fan 28connects to low-pressure shaft 20. A hot section 30/18/24 extendsbetween a combustor 30 and a low-pressure turbine 18, and includeshigh-pressure turbine 24. In the illustrated embodiment, hot section30/18/24 of gas turbine engine 10 includes an augmenter 32. The generalconstruction and operation of gas turbine engines is understood in theart, and therefore detailed discussion here is unnecessary.

Working fluid enters low-pressure compressor 16 and is compressed bylow-pressure compressor 16. The working fluid then enters high-pressurecompressor 22, which further compresses the working fluid. The workingfluid then enters combustor 30 where it is mixed with fuel and ignited,forming hot high-pressure combustion gases. The working fluid thereafterflows through high-pressure turbine 24 and low-pressure turbine 18 whichexpand the working fluid, extracting work, and rotating low-pressureshaft 20, high-pressure shaft 26 and fan 28 about a rotation axis A.Rotation of the low-pressure shaft and high-pressure shaft 26 compressesworking fluid flowing through the engine and rotation of fan 28 providesthrust to a vehicle coupled to gas turbine engine 10, such as anaircraft. Additional fuel can be added to combustion gases exitinglow-pressure turbine 18 in augmenter 32, generating additional thrustand exposing engine structure within augmenter 32 to extremely hightemperatures.

With reference to FIG. 2, a portion of hot section 30/24/18 is shown.Hot section 30/24/18 includes an interior liner 50 (e.g. a hot sheet),an exterior liner 52, and a coupling member 54. Interior liner 50 is ahot sheet and is bounded on one side by a hot gas space 56. Exteriorliner 52 is a cold sheet and substantially envelopes interior liner 52for separating engine components (shown in FIG. 1) from combustion gasspace 56. Interior liner 50, exterior liner 52 and coupling member 54are constructed from a material suitable for extreme temperatureenvironments such as a nickel alloy. One such alloy is Inconel®,available from Inco Alloys International, Inc. of Huntington, W.V.

A coolant plenum 58 is defined between interior liner 50 and exteriorliner 52. Coolant plenum 58 is bounded by an inner surface 60 ofexterior liner 52 and an outer surface 62 of interior liner 50. Coolantplenum 58 is fluidly coupled to a coolant source, e.g. low-pressurecompressor 16 or high-pressure compressor 22, and is configured andadapted direct coolant extracted from the coolant source across outersurface 62 for purposes of cooling interior liner 50. In the illustratedembodiment, a coolant flow enters coolant plenum 58 through an inlet 64defined in exterior liner 52 fluidly coupled to the coolant source andis distributed about outer surface 62 of interior liner 50. Coolantflows from coolant plenum 58 into combustion gas space 56 through atleast one channel defined in interior liner 50, thereby providing acoolant boundary layer adjacent an interior surface 66 of interior liner50. This allows for operating hot section 18/24/30, and in engines soequipped, augmenter 32, with an interior temperature above thetemperature at which the mechanical properties of the material of whichinterior liner 50 are stable. As will be appreciated by those skilled inthe art, other configurations are possible within the scope of thepresent disclosure.

Coupling member 54 couples interior liner 50 to exterior liner 52.Coupling member 54 has a sheet-like structure and includes a pluralityof folds 68 along its longitudinal length between outer surface 62 ofinterior liner 50 and interior surface 60 of exterior liner 52. Withreference to fold 68 adjacent outer surface 62 of interior liner 50,fold 68 defines a terminal portion 70 of coupling member 54 disposedover outer surface 62 of interior liner 50. In the illustratedembodiment, coupling member 54 is a Z-band. As will be appreciated bythose skilled in the art, coupling members of other types are within thescope of the present disclosure, such as an S-band 74 or differentlyshaped coupling member (also shown in FIG. 2).

With reference to FIG. 3A, a lap joint formed by welded assembly 100 isshown. Liner 50 forms a first sheet 102. A terminal portion of couplingmember 54 forms a second sheet 104 disposed a portion of first sheet 50.An overlap region 106 is defined within the boundaries of first sheet 50between first and second sheets 50 and 70. A weld 108 defined withinoverlap region 106 couples second sheet 104 to first sheet 102. Weldedassembly 100 is formed from first sheet 102, second sheet 104 and alinear weld 108 joins coupling member 54 to interior liner 50, therebydefining a hot sheet joint. A similarly constructed welded assembly 100can be formed on an opposite end of coupling member 54 at its connectionpoint with exterior liner 52, thereby defining a cold sheet joint.

With reference to FIG. 3B, linear weld 108 is shown. Weld 108 has alinear shape and traces a linear weld line 110 extending laterallyacross second sheet 102. Weld line 110 extends parallel to a bend line112 defined by fold 68, weld line 110 being offset from bend line 112 bya first longitudinal offset distance A. Weld line 110 is also laterallyoffset from a lateral edge 114 of second sheet 102 by a lateral offsetdistance B. Weld line 110 is additionally offset from a longitudinaledge 116 on an opposite side of weld 108 by a second longitudinal offsetdistance C. During operation interior liner 50 and exterior liner 52 canbe exposed to different temperatures and expand at different rates. Thisimposes a shear force F (shown in FIG. 2) on welded assembly 100 thatimposes stress in the joint formed by the assembly. This stress canexceed that tolerable by welds formed using conventional weldingprocesses. For that reason, and for the need to join structuresfabricated from materials less amenable to conventional weldingprocesses, conventional hot sheet to Z-band joints are using a brazingprocess. Embodiments of the welded assemblies described herein utilizewelds with functional, geometrically defined weld patterns that moreevenly distribute that conventional welds, thereby reducing weld stressand avoiding (or reducing) use brazes in such hot sheet and/or coldsheet joints. For example, linear weld 108 is configured and adapted todistribute stress within welded assembly 100 such that force F imposes astress distribution 150 (shown in FIG. 3C) having the contourillustrated and with peak stress occurring at opposite ends of linearweld 108. In an exemplary embodiment of welded assembly 200, first andsecond longitudinal offset distances A and C are about 1.5 times lateraloffset distance B, thereby producing the stress distribution 250illustrated in FIG. 4C.

Turning now to FIG. 4A, welded assembly 200 is shown. Welded assembly200 is similar to welded assembly 100, and additionally includes anarcuate weld 208. With reference to FIG. 4B, arcuate weld 208 traces anarcuate weld line 210 within overlap area 106 including at least onearcuate segment 216. In the illustrated embodiment, arcuate segment 216is a first arcuate segment and arcuate weld 208 further includes asecond arcuate segment 218 and a third arcuate segment 220. Secondarcuate segment 218 is formed on an end of first arcuate segment 216 andthird arcuate segment is formed on an opposite end of first arcuatesegment 216, thereby forming a continuous weld having a plurality ofarcuate weld segments 216, 218 and 210.

Arcuate weld line 210 is offset from a bend line 112 defined by fold 68,arcuate weld line 210 being offset from bend line 112 by a firstlongitudinal offset distance A. Arcuate weld line 210 is also laterallyoffset from a lateral edge 114 of second sheet 102 by a lateral offsetdistance B. Arcuate weld line 210 further defines a linear segment Cparallel with respect to bend line 112 in each of arcuate segments 216and 218. In an exemplary embodiment of welded assembly 200, longitudinaloffset distance A and lateral offset distance B are about twice thelength of linear segment C and the main bend radii is about three timesthe staple bend radii.

With reference to FIG. 4C, force F induces stress within the exemplaryembodiment of welded assembly 200 with a stress distribution 250 andillustrated stress contours. Notably, the area within welded assembly200 through which stress is distributed in larger than that associatedwith welded assembly 100. Points of relative peak stress are alsolaterally inward with respect to lateral ends of weld 208 as compared toweld 108. For a given force F, peak stress imposed within weldedassembly 200 is about 65% of peak stress imposed within welded assembly100. Redistributing stress, as well as shifting and reducing peak stressmake the stress resultant from force F on welded assembly 200 moretolerable and allow for construction of joints between hot sheets andZ-bands without brazes.

Turning now to FIG. 5A, a welded assembly 300 is shown. Welded assembly300 is similar to welded assembly 100 and additionally includes anarcuate weld 308. Weld 308 has an elliptical shape and fastens secondsheet 104 to first sheet 102 and is defined within overlap area 106.Weld 308, second sheet 104 and first sheet 102 form a joint includingwelded assembly 300 such for fixing a hot gas space liner within a gasturbine engine for example.

With reference to FIG. 5B, weld 308 includes a weld line 310. Weld line310 traces a segment of an ellipse, and in the illustrated embodimenttraces about a side portion of an ellipse bisected by a major axis 320of the ellipse. A minor radius 322 of the ellipse has a length C that isabout four times longitudinal offset distance A. Minor radius 322 isabout three quarters the length of lateral offset B between a lateralend 324 of weld 308 and a lateral edge 326 of second sheet 104

With reference to FIG. 5C, a stress distribution 350 associated withforce F within welded assembly 300 is shown. For a force F, peak stresswithin welded assembly 300 is about 25% of peak stress with weldedassembly 100. An area of welded assembly 300 within which stress isdistributed is greater than that of stress distributions 250 and 150.Peak stress occurs along an interior segment of weld 308, over a lengthof the weld instead of at points of peak stress as is the case withwelds 108 and 208. Redistributing stress, and further shifting andreducing peak stress make the stress resultant from force F on weldedassembly 300 more tolerable. This allows for construction of jointsbetween hot sheets and Z-bands without brazes.

In an exemplary embodiment, weld line 310 is offset from bend line 112by a distance about 4.16 times the length of the minor radius of theellipse and an end of the weld line is offset from lateral edge 326 by adistance about 6.6 times the length of the minor radius of the ellipse.This reduces peak stress in weld 308 to about 25% of peak stress inlinear weld 108. As will be appreciated, the relative amount of stressimprovement is influenced by other factors in additional to weldgeometry, such as the total weld area and total weld length for example.

With reference to FIG. 6, a plot of normalized weld stress is shownalong respective lengths of linear weld 108, arcuate weld 208, andelliptical weld 308. Peak stress in arcuate weld 208 is reduced by about40% in relation to peak stress in linear weld 108 as well as shiftedinwards from respective ends of arcuate weld 208 in relation to weld108. This makes arcuate weld 208 more reliable when subjected to forceF. Peak stress in elliptical weld 308 is further reduced, being about25% of that within linear weld 108. Peak stress is also shifted inwardsand distributed over a greater length of weld 308 in comparison tolinear weld 108 and arcuate weld 208. This provides additionalimprovements in reliability when subjected to force F.

Embodiments of the welded assembled described herein provide assemblieswith reduced weld stress for a force, weld length and weld area throughthe weld geometries described above. These geometries provide weldedassemblies with better weld (and assembly) stress distribution and peakstress without requiring additional welding time, expense or risk of anenlarged heat affected zone. Embodiments of the welds described hereinalso provide for rapidly fabricating consistent welds using a laser asthe geometry is continuous. This allows for continuously forming theweld by welding without having to alter the output power of the laser.As lasers are more easily controlled at constant output power,continuous weld geometries as described herein allow for welding atconstant output power for producing a relatively consistent weldstructure within the overlap area.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for welded assemblies with superiorproperties including reduced peak stress and more uniform stressdistribution across the welded joint for a given load. While theapparatus and methods of the subject disclosure have been shown anddescribed with reference to preferred embodiments and in the context ofan augmenter (i.e. an afterburner), those skilled in the art willreadily appreciate that changes and/or modifications may be made theretowithout departing from the spirit and scope of the subject disclosure.For example, the apparatus and method described herein are also suitablefor use on other engine structures such as combustors and nozzleassemblies for example.

What is claimed is:
 1. A welded assembly, comprising: a first sheet; asecond sheet disposed over a portion of the first sheet, wherein anoverlap area is defined where the first and second sheets overlap; and aweld disposed within the overlap area, wherein the weld connects thefirst sheet to the second sheet and is configured and adapted fordistributing stress within the weld and overlapping portion of thesecond sheet.
 2. A welded assembly as recited in claim 1, wherein thesecond sheet is a coupling member for supporting a structure disposed ina gas turbine engine.
 3. A welded assembly as recited in claim 1,wherein the first sheet is a hot sheet disposed within a gas turbine hotsection.
 4. A welded assembly as recited in claim 1, wherein the firstsheet is a cold sheet of a gas turbine.
 5. A welded assembly as recitedin claim 1, wherein the second sheet is a z-band coupling a hot sheet toa cold sheet of a gas turbine engine.
 6. A welded assembly as recited inclaim 1, wherein the weld includes a weld line tracing a straight linesegment in the overlap area.
 7. A welded assembly as recited in claim 1,wherein the weld includes a weld line tracing an arcuate segment in theoverlap area.
 8. A welded assembly as recited in claim 7, wherein thearcuate weld line arcuate segment is a first arcuate segment, whereinthe weld line further traces a second and a third arcuate weld linesegment disposed on opposite ends for the first arcuate segment andhaving curvatures different than that of the first arcuate segment.
 9. Awelded assembly as recited in claim 1, wherein the weld includes a weldline tracing an elliptical segment in the overlap area.
 10. A weldedassembly as recited in claim 9, wherein the second sheet includes alaterally extending bend line parallel to a major axis of the ellipse.11. A welded assembly as recited in claim 9, wherein the ellipticalsegment opens in direction opposite bend line.
 12. A welded assembly asrecited in claim 10, wherein a distance between the weld line and thebend line is about a quarter the length of the minor radius of theellipse.
 13. A welded assembly as recited in claim 10, wherein an end ofthe weld line is offset from a lateral edge of the second sheet by adistance about one and a half times the minor radius of the ellipse. 14.A welded assembly as recited in claim 9, wherein the elliptical weldline segment is centered with respect to a loading axis of the secondsheet.
 15. A welded assembly as recited in claim 1, wherein the weldedassembly is a lap joint.
 16. A gas turbine engine hot section,comprising: a welded assembly as recited in claim 1, wherein the firstsheet is a combustion gas space liner and the second sheet is a z-bandfor fixing the liner within the gas turbine engine; wherein the weldincludes a weld line tracing an elliptical segment in the overlap area;wherein the second sheet includes a laterally extending bend lineparallel to the major axis of the ellipse, the elliptical segmentopening in direction opposite the bend line; wherein a distance betweenthe weld line and the bend line is about a quarter the length of theminor radius of the ellipse; wherein a distance between an end of theelliptical segment and a lateral edge of the second sheet is about oneand a half times the length of the minor radius of the ellipse; andwherein the elliptical segment is centered with respect to a loadingaxis of the second sheet.
 17. A hot section as recited in claim 16,wherein the weld is configured such that the peak stress within the weldoccurs laterally inward from an end of the weld.
 18. A method of forminga welded assembly, comprising: overlapping a first sheet with a secondsheet; and forming a weld fastening the first sheet to the second sheetby tracing an elliptical weld line in an overlap area defined betweenopposed contacting surfaces of the first and second sheets, wherein theweld is formed using a laser welding process.
 19. A method as recited inclaim 18, wherein the second sheet includes a bend line and the methodfurther includes defining the weld line an offset distance about aquarter of the minor radius of the ellipse.
 20. A method as recited inclaim 18, further including defining the weld line offset about one anda half times the minor radius of the ellipse from an edge of the secondsheet.